For many decades self-propelled combine harvesters have been used by farmers to harvest a wide range of crops including cereals, maize and oil seed rape. Typically a combine harvester cuts the crop material, threshes the grain therefrom, separates the grain from the straw and cleans the grain before storing in an on-board tank. Straw and crop residue is ejected from the rear of the machine.
The crop processor of a combine harvester comprises threshing and separating apparatus. The separating apparatus is traditionally based upon one of two well-established systems. In a first known system straw walkers are used to ‘walk’ the crop stream rearwardly in the combine wherein agitation caused by this movement causes the grain to fall through an integrated grate whilst the straw residue falls from the rear and out of the combine. In the second alternative system cylindrical rotors are mounted within the combine longitudinally and enclosed by rotor cages wherein crop fed in at the front travels rearwardly in an axially spiral motion due to interacting crop engaging elements fitted to the rotor tube and guide vanes fitted on the inside of the rotor cage. The cylindrical rotors can provide a threshing and separating action, or a separating action only. Separated grain falls through a grate in the cage whilst the straw residue is conveyed rearwardly and out of the machine. The invention is concerned with this second system of separating apparatus.